I did my usual bicep curls and tried a new thing targeting the triceps where the weight is behind one's back and elbows point straight up towards the ceiling, no idea what it's called. It felt kind of nice to do and definitely felt effective
I assume you mean an overhead tricep extension ?
https://exrx.net/WeightExercises/Triceps/DBOneArmTriExt
yes, it is a normal exercise as @LaMaria said but it is easy to overload it too much. I prefer a french press in the lying position but it can be done standing or seated. Similar to a Skull Crusher but the bar comes down behind the head. however all of these exercises require good shoulder mobility if you don't have that then anything over and behind the head is not a good option in which case skull crushers are a better option.